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Baby feet: Toddler bones show pre-human kids scampered up trees

“To have a fossil this complete, and to have the fossil of a child, gives us a brand-new window into of what it was like 3 million years ago.”

At left, the 3.32 million-year-old foot of an Australopithecus afarensis toddler shown from different angles. At right is the child's foot, bottom, compared with the fossil remains of an adult Australopithecus foot, top.Jeremy DeSilva and Cody Prang

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The foot bones of a toddler who died 3 million years ago show that baby pre-humans could both walk upright like modern humans and scamper up trees like apes, researchers said Wednesday.

The thumb-sized fossils come from a skeleton discovered in Dikika, Ethiopia, in 2002 and they have delivered priceless insights into how modern humans evolved from our distant ancestors, the researchers said.

“To have a fossil this complete, and to have the fossil of a child, gives us a brand-new window into of what it was like 3 million years ago,” said Jeremy DeSilva, a paleontologist at Dartmouth University whose team examined the tiny foot bones.

The bones have been dated to about 3.3 million years ago and identified as the same species as “Lucy”, the most famous example of an Australopithecus. The toddler bones date to about 200,000 years earlier than Lucy’s, however.

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Also, having infants and toddlers that could hold on tight, without having to be carried, would make it much easier for the parents to move around. “Another thing they didn’t have 3 million years ago was strollers,” DeSilva said.

Modern human babies are born with feet already made for walking, but Australopithecus could have developed strong walking feet in another way, DeSilva said — by using them that way.

“Bones are living tissues. They grow and respond and they change shape depending on what you do to them,” he said. “Even though humans and Lucy’s kind as adults have chunky heels, we developed them in completely different ways. We would never have known that without this fossil.”

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DeSilva, who has twins who were themselves toddlers when he started studying the fossil, says he feels a special attachment to it.

“This was a toddler who died and it’s really hard to think about when you have your own toddlers,” he said. “And yet it is giving us this absolutely extraordinary amount of information about our past and about why we are the way we are today.”